Brightness and Stars
What do we call how bright a star looks to us from Earth?
Apparent Brightness
What causes day and night on Earth?
The Earth's rotation on its axis
What unit of measurement do scientists use to measure distances inside our Solar System?
Astronomical Units (AU)
What is the name of the galaxy that contains our Solar System?
The Milky Way
What is the word for the tendency of an object to keep moving the same way unless something else acts on it?
Inertia
Why does the Sun appear brighter than other stars in our sky?
Because the Sun is much closer to Earth than other stars.
How many hours does it take Earth to complete one full rotation on its axis?
24 hours
Which planet is third from the Sun?
Earth
What shape is the Milky Way galaxy?
Spiral
What causes the seasons on Earth?
Earth's tilt on its axis
What is one reason two stars could have different apparent brightness besides distance?
The star could be larger/ hotter (intrinsically brighter) or smaller/cooler (intrinsically dimmer).
What is the line where the Earth and sky seem to meet?
The horizon
Name one unique feature of Earth that helps life exist on its surface.
Liquid water on its surface.
Which galaxy is the closest to the Milky Way that we can see with our eyes?
Andromeda galaxy
How long does it take for Earth to revolve around the Sun?
one year
A star that looks dim from Earth could actually be very bright but far away. What term describes how bright a star truly is?
Absolute brightness/luminosity
Describe how and why shadows change length from morning to noon to evening.
Shadows are long in the morning, shortest at noon, and long again in the evening because the Sun appears lower on the horizon in morning and evening and highest at noon.
What keeps the planets following paths around the Sun instead of flying away?
Gravity
Scientists estimate that there __________ of galaxies in the universe.
trillions
Why do shadows point in different directions during the day?
Because Earth’s rotation makes the Sun appear to move across the sky, and as the direction from which sunlight comes changes, so shadows rotate.
How does distance affect a star’s apparent brightness?
As distance increases, the same light spreads out more, so the star appears dimmer.
What angle is Earth tilted at on its axis? Give the number of degrees.
23.5 degrees
In what shape do planets orbit around the Sun in our solar system?
Elliptical (oval) shape
Name the galaxy where scientists photographed a supermassive black hole.
Messier 87 (M87) — the supermassive black hole there was the first black hole imaged.
Explain gravity's role in space and on Earth.
It holds planets in orbit and pulls objects down toward the center of the Earth.